JP2004222284A - Improvement of scanning head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning head which is compact, inexpensive and capable of operations in multiple modes and substantial safety operation using an internal LED light source, has various uses and is capable of operating with high sensitivity and high accuracy even for a medium of low contrast. <P>SOLUTION: The scanning head to be used in a register mark detection apparatus for detecting a register mark on a web is provided appropriately for a relative motion between the web and the scanning head. Further, the scanning head is equipped with a photo-sensor and a first optical mask having an aperture for specifying a field-of-view footprint of the photo-sensor via the photo-sensor. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a scanning (scanning) head and an improvement thereof, for example, a scanning head such as a scanning head used in the printing (printing) industry for detecting a print (register) mark or for recording a folding line. Regarding its improvement. The scanning head may have a movable scanning component, or more usually, for applications in the printing industry, may be a stationary module without a movable component, where it is monitored. The mark to be placed is on a substrate, such as a print web, which is moved past a scanning head. The scanning head may have one or more optical sensors. The invention further relates to a print recording unit for a printing press and a method for recording prints.

  With the rising raw materials and overall production costs and margins of profit in the printing industry being compressed, the industry needs to implement cost savings where possible.

  One area where technological advances have resulted in cost savings is in the design of printing presses (print presses) and print recording (register) devices. Improvements in print recording equipment ensure, for example, that each color layer in a four-color printing process is more reliably printed on a register (recorder) with respect to each other as they are implemented on the print web in sequence. By doing so, the wear in running each print has been reduced as much as possible, and significant savings have been realized. Examples of such an improvement of the print registration device are described in European patents EP0340897 and EP0403082. In each case, one or more rows of optical sensors are provided in one or more scanning heads that cover the print web to detect print registration marks on the print web, and the process of connecting to the scanning heads. The device (processor) monitors signals from the sensors to determine the time at which a sensor or group of sensors has detected the passage of a print record mark.

  Many improvements have been obtained in the operational efficiency and effectiveness of print recorders, but hardware costs have not been effectively saved. Accordingly, one primary object of the present invention is to provide a more economical construction of a print recorder, while maintaining the high standards of accuracy and reliability that the printing industry has expected and required. Another main object of the present invention is to provide a more compact structure of the print record scanning head.

  According to a first aspect of the present invention, there is provided a scanning head suitable for use in a recording mark detection device for detecting a recording (register) mark / shape on a web surface or another surface, comprising: Appropriately used in relative movement between the scanning head and the scanning head, further defining an optical sensor and, via it, a view footprint of the optical sensor. A first optical mask having an opening.

  Instead of a focusing lens or mirror, the optical mark acts to define the footprint of the field of view of the optical sensor, i.e. the field delimits that part of the sensory surface of the optical sensor to be illuminated. If any lens is in the path of the received light, this is simply the lens surface of the optical sensor. If any mirrors are in the path of the received light, this will only redirect appropriately, but will not focus the light at the focal point.

  The field-of-view footprint of the optical sensor is suitably substantially smaller than the perceived area of the optical sensor, and the scanning head is in use equal to or larger than the area of a recording mark on the web viewed by the scanning head. It is preferably formed for the purpose of viewing the area of the web which is the same (the field of view footprint of the web).

  The first optical mask is preferably located at or near an optical opening to the scanning head, particularly in use in a plane very adjacent to and parallel to the web. preferable.

  In a preferred embodiment, said first mask is smaller than 10 mm and preferably in use between 3 and 5 mm from said web.

  Suitably, the scanning head further comprises a light source for illuminating the visibility footprint of the web, wherein the light source is preferably a solid state, low power light source, further comprising: It is particularly preferred to have more than one LED.

  Preferably, the scanning head comprises a light source disposed in the scanning head to form a straight reflection illumination of the web. For suitably transparent web media, a mirror is provided in combination with the scanning head and is mounted on the opposite side of the web from the scanning head to direct light through the web to the scanning head. Reflect back.

  Preferably, the scanning head comprises a light source disposed on the scanning head to provide diffuse illumination of the web.

  In one embodiment, the scanning head has a white light source and the sensor is configured to detect light across the visible spectrum.

  The scanning head preferably has a UV light source, and the sensor is preferably a UV sensor.

  Preferably, the scanning head comprises a plurality of light sources, which may be selected either to be used independently or to be used together. Suitably the at least two light sources differ from each other in the wavelength of the emitted light.

  Preferably, at least one of the plurality of light sources is disposed in the scanning head to form a straight reflection illumination of the web, and the other light source is disposed in the scanning head and the light source of the web. Preferably, diffuse illumination is formed.

  It is particularly preferred that the scanning head has a second mask having an opening in series with the first mask. This further forms a visibility footprint of the optical sensor that improves sensitivity and accuracy. Further, the use of multiple masks promotes scanning of different light wavelengths, rather than wavelength sensitivity.

  In use, the second mask is preferably located between the first mask and the sensor, preferably closer to the sensor as compared to the distance to the first mask, and further to the web It is preferable that the distance between the first mask and the first mask is sufficiently close to the sensor.

  Preferably, the space between the first mask and the second mask is larger in use, on the order of ten times the distance from the web to the first mask. It is preferable that the area of the opening of the second mask is larger than the area of the opening of the first mask, and the first and second masks have a distance from the web to the first mask. Preferably, the ratio is substantially the same as the ratio of the intervals.

  The openings in the mask, or at least one opening of the mask when two masks are present, may be formed in use with a shape that is the same as or similar to the shape of the recording marks found on the print web. Particularly preferred. The openings in the mask, or at least one opening of the mask when two masks are present, are of a shape that is synthetic, i.e. not just a single line or square or circular, but a number of lines or portions (e.g. , A star shape or an L or U shape) or a shape having a number of holes or slots / slits. These improvements also improve the accuracy and reliability of recording mark detection.

  Suitably, the scanning head is formed to allow removal of the mask and allow replacement with a mask having a different opening shape or size.

  According to a second aspect of the present invention, there is provided a print recording device (apparatus) of a print press comprising a scanning head of the first aspect of the present invention, and in accordance with a third aspect of the present invention, such a print. A print press (printing machine) including a recording device is provided. The print recording device has or is operatively connected to a processing unit for monitoring signals from one or more sensors of the scanning head for detecting recording.

  The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which:

  Referring first to FIG. 1, this illustrates the principles of the present invention, which suitably shows a scanning head optical sensor 1, such as a photosensitive diode, said optical sensor 1 being mounted on a print web 4. And receives light reflected back from a small portion / view footprint 5 of the web 1 that is properly positioned and slightly larger than the footprint of the recording mark on the web 4.

  In stark contrast to conventional scanning heads, there are no expensive focussing lenses or mirrors spaced apart from the optical sensor 1 for focusing light on the optical sensor 1, but The sensor 1 may have a small integrated light receiving lens as shown in the figure. Instead of expensive separate lenses or focusing mirrors, the scanning head has a sensor 1 with a high forward gain (input / output ratio) and a narrow beam width (e.g. 10 degrees) and an optical sensor. A pair of optical masks 2, 3 located between 1 and web 4 are used to prevent stray light from reaching sensor 1.

  Each of the masks 2, 3 has a respective opening 6, 9 so that as the recording mark passes near the sensor 1, the sensor 1 will move the web 1 approximately corresponding to the footprint of the recording mark 5 on the web 4. Only the light reflected from the small viewing area 5 of Each opening 6, 9 is shown to be an elongated slot-shaped opening. This suitably corresponds to the shape of the recording marks used on the print web 4.

  With respect to the first mask 2, which is closest to the web 4, the dimensions of the openings 6 are suitably the same as the visibility footprint 5 on the web 4.

  The first mask 2 is placed in a plane parallel to the web 4 and is spaced from the web 4 by a very short fixed distance on the order of a few mm. The first mask performs the main identification of the recording marks 5 and is almost entirely in focus as a result of being so close to the print web 4. In the illustrated example, the first mask 2 is spaced apart from the web 4 by only 4 mm and has a 0.5 x 0.8 mm opening 6 corresponding to a 0.5 x 0.8 mm viewing area 5.

  During the running of the print, the print web 4 performs an oscillating motion known as a print flap, the oscillating motion having a magnitude determined by the mass and the tension (tensile force) and the moving speed of the moving print web 4, Since the distance from the web 4 to the first mask 2 is periodically changed, the positioning height tolerance of the preferred scanning head (tolerance of the distance from the print web 4 to the first mask 2) is 3 mm +/- 1 mm. It is.

  The second mask 3 is set within a range of a few mm from the sensor 1 and within a range of 40 mm away from the first mask 2 and is aligned with the first mask 2 and the sensor 1. The light reflected from 4 and passed through the opening 6 of the first mask 2, should then pass through the opening 9 of the second mask 3 and reach the sensory surface of the sensor 1.

  As shown in FIG. 1, the light reflected from the web 4 is restricted by the first mask 2 to a beam within the boundaries of the upper 7 and lower 8 boundaries. In the plan view of FIG. 2, the lateral boundaries of the beam are indicated by boundaries 11, 12. The shadow (umbra) 13 and penumbra (penumbra) 14 of the target footprint / real image area 5 on the print web 4 intersect (crossover) as the light passes through the aperture 6.

  The second mask 3 limits the light input to the sensor 1 while allowing sufficient light with a better signal to noise ratio. Since the required final optical footprint is generally not similar to the large aperture circular receiving lens / sensing (sensor) surface of the sensor 1 and is small and non-circular, the second mask 3 is It helps to optimize the fit between the footprint defined by the mask 2 and the large-diameter circular light receiving lens / sensing (sensor) surface of the sensor 1.

  In order to optimize the overall sensitivity and selectivity of the receiver (receiver), the area of the opening 9 of the second mask 3 is of the dimension 2 (the distance between the masks 2, 3) and the dimension 2 (on the web 4). To the area of the opening 6 of the first mask, corresponding to the ratio (scanning head height) of the first mask, and that (the ratio of dimension 1 to dimension 2) is of the order of 10: 1. Is preferred. Assuming that the dimension 1 in the illustrated example is 40 mm, the dimension 2 is 4 mm, and the area of the opening 6 is 0.5 mm × 0.8 mm, the selected dimension of the opening 9 is suitably 1 × 4 mm, ie, the opening 6 10 times larger than the area of

  With a proper choice of the dimensions of the mask openings 6, 9 and the ratio of the dimensions 1 and 2, the visibility footprint 5 is reduced to a very small area. Further optimization is achieved by forming the openings 6, 9 in the shape of the recording marks to be detected. The illustrated 0.5 x 0.8 mm aperture 6 in the first mask 2 can be, for example, a single 0.1 x 4 mm slit suitable for the application where the print record mark is a line, without changing the overall field of view footprint area 5. It may be adjusted. For a star-shaped print record mark, the aperture 6 is also suitably star-shaped. This can further improve the reliability of recording mark detection.

  The aperture 6 can be constituted by an array or group of small apertures, which reproduces an array or group of discrete elements / or lines with synthesized print recording marks. (Replicate) is formed. For example, two parallel slots (holes) comprising openings 6 in the mask 2 may be present on the print web 4 corresponding to the two parallel lines of the print record mark, which furthermore , Provides greater reliability of print registration as compared to a single slot corresponding to a single line mark.

  For applicability in applications, the apparatus is suitably formed so that the mask 6 and the mask 9 can be exchanged, so that they can be replaced by a mask having another shape or form of opening.

  Referring to FIG. 3, the preferred embodiment of the scanning head has a compact structure with masks 2, 3 and sensor 1 held in a housing 20 in the same relative position as in FIGS. However, the line between the first mask 2 and the second mask 3 is folded by a simple low cost (non-focusing) mirror 18 to make the head even more compact. It is in a state.

  For optimal versatility, one or more sensors 1 and masks 2, 3 may be removable from housing 20 and / or they may be positionable within housing 20 and The head may be adjustable by the user for special needs.

  To illuminate the field of view footprint area 5 of the print web 4, the scanning head serves as a light source, a pair of wide-angle, wide-angle, mounted in a housing adjacent to the receiving (light) components (sensor 1 and masks 2, 3). It has LEDs 15, 16 but is shielded from them by a barrier wall 19. These two LEDs 15, 16 may be substantially identical and may emit light of the same wavelength and intensity with respect to each other, but they differ in their installation angle within the housing 20 and the scanning It is important to enable the head to have two main different modes of operation.

  The first LED 15 is for operation in the divergent mode, and is installed in the housing 20 with its axis inclined at 45 degrees with respect to the normal to the bottom surface of the housing 20, whereby the web 4 It is at 45 degrees to the normal, because the bottom surface of the housing 20 is a plane parallel to the web 4. This first LED 15 therefore does not have a direct reflection path through the medium / print web 4 to be scanned into the optical receiver window through the opening 6 of the first mask 2. . It functions to provide a diffused light source for scanning operations, which is particularly suitable for detecting recording marks on printing paper, holograms and embossed media.

  The second LED 16 is for operation in the straight reflection mode, and is installed in the housing 20 with its axis inclined at 10 degrees with respect to the normal to the bottom surface of the housing 20, whereby the web 4 At a 10 degree angle with respect to the normal line, and promotes direct reflection from the web 4 to the optical receiver window. This LED 16 is particularly useful for scanning reflective media or printed marks on transparent media. In the latter case, a mirror backing plate 17 located below the transparent medium may be used to reflect light to the optical receiver window. In the operation of the second LED 16, the angles of incidence and reflection through the optical path from the LED 16 of the luminescent light source to the optical light receiver / receiver 6 are equal.

  The height of the scanner head and the location of the LEDs are properly designed so that the area of the print web 4 illuminated by the LEDs is of sufficient size to accommodate the visibility footprint / mask aperture 6 footprint. , And in that case, additional tolerances are designed to be created for the height tolerances of the scanner head and the web flap described above.

  The scanning head is formed to allow selection of a switch between light source / operation modes, with the first or second LED 15, 16 being selected depending on the medium to be scanned. In fact, simultaneous mixing of light from both the first and second LEDs 15, 16 may be used to suit some media, and to maximize the versatility of the light source. The wavelength and intensity can be adjusted appropriately. To this end, the first and second LEDs 15, 16 may each be part of a respective group of LEDs, ie one group has a 10 degree or similar angle for a straight reflection operation. And the other group has a 45 degree or similar angle with respect to the diffuse light operation, wherein the LEDs of each group differ from each other in wavelength output and may be individually in a single application or in combination with another. Can be selected.

  For example, one of the LEDs in each group may emit light of one particular visible spectrum of color, such as red, for example, while another emits light of a different specific visible spectrum, such as green. It may be UV light, if it emits colored light, or in one particularly preferred design, the sensor 1 incorporates a UV optical receiver.

  Alternatively, a white light LED can be used where the received light sensor 1 is an eye color responsive detector (detector) configured to detect light that crosses the entire visible spectrum. When the LED emits light of one particular visible spectrum color, said color is appropriately compared to the underlying medium of the field of view, increasing the detection sensitivity and making it possible to detect very light shades . One color or a combination of colors may be used to optimize the contrast of the field of view with the underlying medium.

  UV-based detectors allow recording of UV-reflective clear inks, varnishes, lacquers, low temperature seals, glues and other clear media that are not recordable by conventional visible light-based devices To Providing a UV-emitting LED and a corresponding receiver in the scanning head of the present invention is particularly useful, as it provides an exceptionally cost-effective UV-sensing device, wherein the mask 2,3 Avoids the need for multiple quartz lenses, and also allows the scanning head to focus on very small media marks.

  Alternatively or additionally, varnishes, lacquers, low-temperature seals, glues and other clear media may be scanned using white light emitting LEDs and appropriately adjusting the level of light from the LEDs. good.

  In operation of the scanning head as part of a print record sensing device or for another purpose, the necessary scanning head functions can be achieved via controlled illumination. The UV mode is a common exception, where the parameters of the light sensor are kept the same for different modes.

  In general, the analog output signal of the receiver / sensor is the contrast ratio and / or embossed relief profile of the medium being scanned, ie, the print web, as viewed in the field of view footprint of the sensor. Outer shape). The analog output signal of the receiver, i.e. the sensor, is appropriately gain-controlled (input-output ratio) so that differences in contrast and reflection performance of different media can be discerned.

  In the example of a print record sensing device, the linear movement of the web raises a time-varying sensor signal as the record mark enters the field of view and subsequently passes through the scanning head. The analog sensor output signal is typically converted to a digital signal by an analog-to-digital converter and then analyzed by a processor / software that is typically part of, or at least operatively connected to, a print record detector. To identify different print record mark features and to activate a subroutine / controller for positional feedback control of the print press. In some devices (systems), the analog signal can be analyzed by an analog processor.

  Beyond the advantages already discussed, the principle of operation of a scanning head that allows the use of very low power solid state lighting is another unique advantage, the inherent nature of a scanning head. Improve safety. It may operate in a potentially explosive atmosphere through approved power limiting protective barriers, unlike conventional scanning heads. Said conventional scanning heads have incandescent / tungsten bulbs, which require more power than can be supplied through such approved power limiting protective barriers. Conventional devices typically use heavy, bulky and expensive explosion-proof casings or long fiber optics to carry light from a remote light source to the outside of the risky compartment, in environments at risk of explosion. It can only be activated by

  Solid state lighting using LEDs also provides dramatic savings in light source maintenance as LEDs have exceptionally high longevity, exceeding 100,000 hours of operational life.

  As mentioned above, the scanning head of the present invention provides a highly effective device for print recording in a print press. The assembly is simple, efficient, efficient, versatile, and very economical in both installation and operation, and lightweight, very compact, and can be used in explosive-risk environments. Yes, and also achieve high standards of accuracy and reliability over a wide range of media. In fact, the ability to fabricate the masks 2, 3 with close tolerances allows for greater accuracy in defining the optical rise and fall times compared to conventional record detectors, and more Achieve high accuracy.

FIG. 1 is a simplified schematic isometric view of components of a scanner head embodying the present invention. FIG. 2 is a plan view of the device shown in FIG. FIG. 3 is a schematic diagram of the components assembled together in a working scanner head.

Explanation of reference numerals

Reference Signs List 1 scanning head optical sensor 2 first mask 3 second mask 4 print web 5 visibility footprint 6 opening 7 upper boundary line 8 lower boundary line 9 opening 15 LED
16 LED
18 Mirror 19 Barrier wall 20 Housing

Claims (24)

A scanning head suitable for use in a recording mark detection device for detecting recording marks / shapes on a web surface or another surface, wherein the scanning head comprises:
An optical sensor;
A first optical mask having an aperture therethrough that defines a viewing footprint of the optical sensor;
A scanning head comprising:   The scanning head of claim 1, wherein the first optical mask is located at or near an optical aperture to the scanning head.   3. The scanning head according to claim 1, wherein in use the first optical mask is arranged in a plane very close to and parallel to the surface.   4. A scanning head according to any one of the preceding claims, wherein the first mask is smaller than 10mm and in use is between 3 and 5mm from the surface.   Suitably, the scanning head further comprises a light source for illuminating a visibility footprint of the surface, wherein the light source is a solid state, low power light source. Scanning head.   The scanning head of claim 5, wherein the light source comprises one or more LEDs. The scanning head includes a light source,
A scanning head according to any one of the preceding claims, wherein the light source is arranged in the scanning head to form a straight reflection illumination of the surface. For transparent web media, a mirror is provided in combination with the scanning head and is located on the opposite side of the web from the scanning head to reflect light through the web to the scanning head. return,
A scanning head according to claim 7. The scanning head includes a light source,
The light source is disposed on the scanning head to provide diffuse illumination of the surface;
The scanning head according to claim 1.   The scanning head according to claim 1, wherein the scanning head includes a UV light source and a UV sensor.   The scanning head according to claim 1, wherein the scanning head has a white light source.   12. The scanning head according to any one of claims 1 to 11, wherein the scanning head comprises a plurality of light sources, the light sources may be selected either to be used independently or to be used together. Scanning head.   13. The scanning head according to claim 12, wherein the at least two light sources differ from each other in the wavelength of the emitted light.   At least one of the plurality of light sources is disposed in the scanning head to form a linearly reflective illumination of the surface, and another light source is disposed in the scanning head for the surface. 14. The scanning head according to claim 12, which forms diffuse illumination.   15. The scanning head according to any one of the preceding claims, wherein the scanning head has a second mask having an opening that is in series with the first mask.   The scanning head according to claim 15, wherein the second mask is closer to and between the first mask and the sensor than the first mask.   17. A scanning head according to claim 15 or 16, wherein the second mask is in use much closer to the sensor than the first mask with respect to the surface web.   18. The scanning head according to claim 17, wherein the space between the first mask and the second mask is larger in use, on the order of ten times the distance from the surface to the first mask.   The area of the opening of the second mask is larger than the area of the opening of the first mask, and the ratio of the distance between the first and second masks to the distance from the surface to the first mask. 17. The scanning head according to claim 16, wherein the scanning head has substantially the same ratio.   2. The opening of the mask, or at least one opening of the mask when two masks are present, is formed in use by a shape that is the same as or similar to the shape of the recording marks seen on the surface. 20. The scanning head according to any one of claims 1 to 19. The opening of the mask, or at least one of the openings of the mask when two masks are present, is of a synthetic shape, i.e. not just a single line or a square or a circle, but also a star shape, for example. Or formed by a shape having multiple lines or portions, such as L or U shapes, or with multiple holes or slots / slits,
A scanning head according to any one of the preceding claims.   22. The scanning head according to any one of the preceding claims, wherein the scanning head is configured to allow removal of the mask and allow replacement with a mask having a different opening shape or size.   A print recording device for a print press, comprising the scanning head according to claim 1.   A print press comprising the print recording device according to claim 23.

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